Prevalence of primary clarithromycin resistance in Helicobacter pylori strains over a 15 year period in Italy

Objectives: The frequency of primary clarithromycin resistance in Helicobacter pylori strains is increasing worldwide, and its presence significantly reduces the treatment efficacy of infection. This study aimed to evaluate whether the progression of the prevalence of clarithromycin resistance over a 15 year period has increased and whether a possible change in the distribution of the three most frequent point mutations, which account for the large majority of clarithromycin resistance cases, has taken place. Methods: Antral biopsies of consecutive H. pylori-positive patients observed between January 1989 and December 1990 and between January 2004 and December 2005 were retrieved. A TaqMan real-time PCR was performed in all cases to assess point mutations involved. Results: Primary clarithromycin resistance was assessed for 147 patients observed in the first period 1989-90 and 178 cases observed in the second period 2004-05. The overall frequency of clarithromycin resistance increased from 10.2% (15 patients) to 21.3% (38 patients) during the study period (P = 0.01). The increase was more evident in females [4 out of 55 patients (7.2%) versus 24 out of 103 patients (23.3%); P = 0.01] and in non-ulcer dyspepsia patients [113 out of 106 patients (12.2%) versus 37 out of 140 (26.4%) patients; P = 0.009]. A2143G was the most frequent point mutation observed in both study periods, and its prevalence rate remained unchanged [11 out of 15 (73.3%) patients versus 27 out of 38 (71 %) patients; P = 1]. Conclusions: A 2-fold increase in primary clarithromycin resistance in H. pylori strains occurred during the last 15 years in Italy. A2143G remains the most prevalent point mutation involved, thus suggesting that new therapeutic strategies are needed.